1. Field of the Invention
The present invention relates to a base structure, a processing device, and an image forming device.
2. Description of the Related Art
In an image exposure device for exposing a light-sensitive material such as a light-sensitive planographic printing plate used for printing or the like (which is referred to as a xe2x80x9cprinting platexe2x80x9d hereinafter), a semiconductor laser, an LED (light emitting diode) or the like is used as a light source, and a light beam emitted from this light source scans and exposes a printing plate. At this time, the light beam is modulated on the basis of image data, and an image is formed on the printing plate.
A light source for exposure provided at such an image exposure device is mounted on a substantially plate-shaped stage integrated with an optical system to thereby form an exposure head. Thus, a light beam emitted from the light source is irradiated from the exposure head onto the printing plate, whereby the printing plate is exposed.
If a distance between the exposure head and the printing plate is not adjusted appropriately, focal displacement may occur in which a spot diameter of the light beam spreads. In order to prevent such focal displacement, sometimes a moving mechanism is provided at the stage at which the light source and the like are mounted to enable the exposure head to approach and move away from the recording medium. Accordingly, the printing plate and the exposure head can be held at an appropriate distance and focused.
An example of the moving mechanism which is applied to such a focusing includes: a moving mechanism in which a fine movement of the stage by about 1 xcexcm, for example, can be performed by using an eccentric cam. In the moving mechanism using such an eccentric cam, a sliding member, a bearing, and the like are disposed at legs which protrude from the stage so as to face the eccentric cam. While the eccentric cam rotates eccentrically, the circumferential surface of the eccentric cam and the sliding member or the bearing abut against one another and press the legs, and the stage thereby moves.
However, when the sliding member is disposed at the eccentric cam, as the eccentric cam rotates, the sliding member is slid with the rotation of the eccentric cam so that abrasion or deformation may cause therebetween, thus leading to an error in a moving amount of the stage. Further, when the bearing is disposed so as to face the eccentric cam, as the eccentric cam rotates, a position at which the eccentric cam contacts the bearing changes, thus leading to a change in the moving amount of the stage.
The most important problem with the moving mechanism using the eccentric cam is that, since another fixing means is provided independently of the moving mechanism in order to fix the stage which has stopped moving, it becomes extremely difficult to move, position, and fix the stage by using the eccentric cam while maintaining the position to which the stage has moved. When the stage thus positioned is fixed by the fixing means, there arises a problem that the stage may be displaced slightly from a desired position at which the stage should be fixed.
In view of the aforementioned facts, it is an object of the present invention to provide a base structure, a processing device, and an image forming device capable of successfully overcoming and improving such drawbacks as described above.
In order to solve the aforementioned problems, a first aspect of the present invention is a base structure, the base structure comprising: (A) two bases between which a linear relative movement is enabled; (B) a cam element provided at one of said two bases and driven to rotate; and (C) an abutting portion provided at the other of said two bases and on which said cam element abuts, (D) wherein said cam element includes: a central axis portion rotatable around a rotational axis as a center; a rolling element movably provided at said central axis portion; and a cylindrical outer ring rotatably provided with respect to said central axis portion through said rolling element, the rotational axes of said outer ring and said central axis portion being substantially parallel to one another and spaced apart from one another at a predetermined distance.
A second aspect of the present invention is a processing device for applying a predetermined processing to an object, the processing device comprising: (I) a processing element for applying a predetermined processing to an object; and (II) a base device capable of changing a position of said processing element with respect to said object, the base device including: (a) a first base and a second base between which a linear relative movement is enabled; (b) a cam element provided at said first base and driven to rotate; and (c) an abutting portion provided at said second base and on which said cam element abuts, wherein said cam element includes: a central axis portion rotatable around a rotational axis as a center; a rolling element movably provided at said central axis portion; and a cylindrical outer ring rotatably provided with respect to said central axis portion through said rolling element, the rotational axes of said outer ring and said central axis portion being substantially parallel to one another and spaced apart from one another at a predetermined distance.
A third aspect of the present invention is an image forming device for forming an image on a printing plate, the image forming device comprising: (I) a rotatably mounted drum having a periphery around which a printing plate can be releasably wound and fixed; (II) a mount for rotatably supporting said drum; (III) a recording head for recording an image on a printing plate; (IV) a base device for changing a position of said recording head with respect to said rotating drum, said base device including: (a) a first base and a second base, one of the bases being fixed at said mount side and the other being fixed at said recording head side, between which a linear relative movement is enabled; (b) a cam element provided at said first base and driven to rotate; and (c) an abutting portion provided at said second base and on which said cam element abuts; (d) wherein said cam element includes: a central axis portion rotatable around a rotational axis as a center; a rolling element movably provided at said central axis portion; and a cylindrical outer ring rotatably provided with respect to said central axis portion through said rolling element; the rotational axes of said outer ring and said central axis portion being substantially parallel to one another and spaced apart from one another at a predetermined distance.